Here in the UK, far right groups such as National front, are banned and membership / association puts you on a police radar. We also have a prevent strategy, which puts a legal duty on teachers for Mandatory reporting under prevent of concerns. If we can step in early then people can hopefully be prevented in to falling in to these hate groups.
We can use a channel process to redirect people to more meaningful activities, the idea is to act before they act by committing a serious offense which gets them a longer crimal record or sanction.
There is a serious concern now about how children as young as 9 are being targeted by these groups, by county lines and many other criminal entities, so they can recruit the next generation, that age group is also vulnerable to child sexual exploitation and or child criminal exploitation.
The US needs to get a grip.